The present invention relates to a decompression apparatus for an internal combustion engine, designed to make starting of the engine easier.
A decompression device has been known which is either automatically or manually operated to open either an intake valve or an exhaust valve to a small extent to reduce the compression pressure in combustion chambers during starting and thereby to reduce the starting load of the engine. In case of a manual decompression device, opening and closing operations of a decompression valve have to be manually carried out.
On the other hand, Japanese Utility Model Publication No. 50-7381 discloses an automatic decompression device which is operated by the centrifugal force of a weight and automatically reduces pressure in a combustion chamber during the starting of an engine. In the known device, the decompression device has a releasing lever with a weight which projects beyond a periphery of a cam by centrifugal force caused by the rotation of a camshaft. However, it is difficult to assemble such a conventional decompression device, since the releasing lever is provided at a position adjacent the camshaft; and production cost becomes higher because of a complicated shape of the releasing lever which must be changed according to the type of the engine.